1. Technical Field
The present invention is related to a board, more specifically to a board a noise shield board that can shield an electromagnetic interference noise by use of an electromagnetic bandgap structure.
2. Description of the Related Art
As the operating frequencies of electronic products become higher, electromagnetic interference (EMI) has become a chronic noise problem. Particularly, as the recent electronic products are operated in a double-digit MHz to a few GHz, the EMI problem has become increasingly serious, making it urgent to find a solution.
An EMI noise refers to a noise that causes a noise problem generated by interference when electromagnetic waves generated in one electronic circuit, device or part is transferred to another electronic circuit, device or part. The EMI noise can be mainly classified into a radiation noise (see reference numerals 110 and 130 in FIG. 1A) and a conduction noise (see reference numeral 120 in FIG. 1A).
In the case of the radiation noise 110 that is radiated through an upper part of a board (i.e., a surface on which an electronic part is mounted), the noise problem is commonly solved by shielding the upper part of the board with an electromagnetic shielding cap, such as a metal cap, or by installing an EMI absorbent on the upper part of the board. However, since it is not possible to install the shield can (see reference numeral 30 in FIG. 1B) or EMI absorbent (see reference numeral 35 in FIG. 1B) on the surface where no electronic part is mounted (i.e., a lower surface of the board shown in FIG. 1B), the shield can or EMI absorbent can not be a solution for shielding the radiation noise 130 radiated to the outside through a surface where no electronic part is mounted.